Scientific Method

“How to think, not what to think”

The scientific method is an orderly and systematic approach to solving problems.

It can be used to solve both scientific and everyday problems.

Steps of the Scientific Method

ObservationDevelop a questionForm a hypothesisPerform an experiment-analyze

dataDraw a conclusion

An everyday problem….

• Sara noticed that she needed a date for Friday night. She is at the observation stage of the scientific method.

• She asked herself..could Ben be my date????

• She is developing the question at this point.

• She hypothesized (made an educated guess) that Ben would indeed be her date.

• To test her hypothesis, she performed an experiment by asking Ben

out on Friday.

Dear Ben,

I really like you. Willyou go out with me thisFriday?Love, Sara

Circle One:Yes, No, or Maybe

• Dear SaraI already have a girlfriend. So I will

notbe able to go out

with you on Friday.

Sorry, Ben

• However, upon analyzing the results of her experiment, she realized that her hypothesis was incorrect and concluded that Ben would not be her date.

• Sara did not give up…..She started over with a new hypothesis.

Maybe Joshwill be my date.

Variable- factor being testedIndependent Variable = What the investigator manipulates; the particular treatment or condition the investigator is most interested in the effects of  Dependent Variable = What is measured or observed; the "data" collected in the experiment Experimental Group = Those participants exposed to the independent variable Control Group = Those participants treated just like the experimental group EXCEPT they are not exposed to the independent variable; the group with which the experimental group can be compared –the factor that responds in a predictable way

Describes how nature behaves but does not explain why nature behaves in that particular way.

It is generally accepted to be true and can sometimes be expressed in terms of a single mathematical equation.

Ex:

Newton’s Laws of

Motion

• Theory: explains why nature behaves in the way described by a natural law

• A theory is more like a scientific law than a hypothesis. A theory is an explanation of a set of related observations or events based upon proven hypotheses and verified multiple times by detached groups of researchers. One scientist cannot create a theory; he can only create a hypothesis.

• Example: Einstein’s Theory of Relativity

Scientific method “situation”

The drug lovastatin was suspected to reduce spasticity (stiffness) in patients suffering from AMN (a neurological disease). In a study, 50 patients were administered lovastatin while 50 other patients were given a placebo.

What is the hypothesis?

Identify the independent variable.

Identify the dependent variable.

Which group represents the control group?

Metric Conversions, Scientific Notation, and Dimensional

Analysis

Scientific Notation

Steps for converting:• Put the decimal after the first digit and drop the

zerosEx. 123,000,000,000 1.23• To find the exponent, count the number of

places from the decimal to the end of the number.

Ex. In 123,000,000,000 there are 11 places therefore we write it as 1.23 x 1011

• Numbers less than 1 will have negative exponents

Ex. 0.000001 will be written as 1 x 10-6

Examples

Convert:• 0.005 • 5,050 • 0.0008• 1,000 • 1,000,000• 0.25 • 0.025 • 0.0025 • 500 • 5,000

International System of Units

• Built on a set of seven metric units, called base units

• Prefixes are added to the names of SI base units to represent quantities that are larger or smaller than the base units

SI Base Units

• Length – meter (m)

• Mass – kilogram (kg)

• Time – second (s)

• Temperature – Kelvin (K)

• Amount of substance – mole (mol)

• Electric current – ampere (A)

• Luminous intensity – candela (cd)

Metric Prefixes and Symbols

• Kilo – k• Hecto – h• Deka – da• BASE• Deci – d• Centi – c• Milli – m

King Henry Died By Drinking Chocolate Milk

Metric Conversions Practice Problems

1. 100m = ____km

2. 3m = ____mm

3. 230cm = ____m

4. 461mm = ____m

5. 2500m = ____km

6. 4500mg = ____g

7. 2000g = ____mg

8. 200g = ____kg

9. 23L = ____mL

10. 0.14mm = ____m

11. 1550mm = ____m

12. 4000mL = ____L

13. 1.4kg = ____g

14. 1452mg = ____g

15. 9.5m = ____cm

Derived SI units

• Area – sq. meter (m2)• Volume – cubic meter (m3)• Density – kg per cubic meter (kg/m3)• Molar mass – kg per mole (kg/mol)• Concentration – moles per liter (M)• Molar volume – cubic meters per mol

(m3/mol)

Dimensional Analysis• The technique of converting between

unitsUses:1. Unit equalities – an equation that shows

how different units are related (ex. 1cm = 0.01m)

2. Conversion factors – equation that always equals one (ex. 1cm/0.01m)*Multiply the conversion factor so that units you do not want cancel and the unit that you do want ends up on top

Unit Equalities (for dim analysis)

2.54cm = 1 in12in = 1ft3ft = 1yd5280ft = 1mi1.6km = 1mi4.184J = 1 cal1000J = 1kJ1km = 1000m1dm = 100mm

Homework Problems

1. 64.5dm = ___ mm2. 91.2m = ___ km3. 96.5in = ___ yds4. 1.235ft = ___cm5. 8.95kJ = ___cal6. 34.5miles = ___m7. 52.3cm = ___ft8. 6.98m/min = ___km/hr9. 59.63cal = ___J10. 96.5kJ = ___cal11. 1year = ___ sec